Diamond drill bit



3 1959 I H. M. CAMERON ETAL 2,911,196

DIAMOND DRILL BIT Filed May a, 1957 NVENTORS arr/y M, Cameron} ag mlmrei K, Hammer WWI-5W ATTORNE 5 to or extends slightly body 11 is threaded United States Patent This invention relates to rock drill bits and more particularly to diamond drill bits of this character intended to provide substantial velocity to all of the abrading sur Y faces with respect to the rock surfaces they are intended to cut.

In conventional drill bits, the cutting velocity of each diamond in the drilling surface is directly proportional to the radius at which it is positioned so that at zero radius, normally the-axis of the drill, the velocity is also zero.

Objects and features of this invention are the provision of drill bit construction intended to provide substantial cutting velocities to diamonds at all radial posit-ions relative to the main drill axis.

In an embodiment of the invention as herein contemplated, this is accomplished by incorporating an auxiliary freely rotatable drill bit with diameter somewhat greater than the radius of the main drill bit and which is positioned relative to the face of the main drill so that it extends beyond the axis or geometrical center of the main bit and so that its peripheryis either tangent beyond that of the main bit. With such arrangement forces for rotating the auxiliary bit are produced by the friction of the rock particles acting both on the auxiliary bit periphery and on its drilling surfaces and the direction of rotation of the auxiliary bit is opposite to that of the main drill bit.

Other objects and features of the invention are the provision of combined main and auxiliary drill bits in a unitary structure that is simple in structure, installation and operation.

Further objects and features of the invention are the provision of appropriate distributing passages for water to both the main and auxiliary bit drilling surfacesto promote efiicient chip removal and heat dissipation.

Other objects and features will become apparent from the following specification and the accompanying-drawing, wherein:

Figure 1 is a longitudinal section taken along line 1--1 of Figure 2; and

Figure 2 is a bottom plan view of the ing the invention.

Referring to the drawing, the reference character generally denotes a rock drill bit embodying the invention. This bit 10 includes a main drill body 11 that is provided with diamond abrading lower and peripheral surface portions adjacent one end of the body. The opposite end of the at 14 as usual for attachment to the A main longitudinally extending water passage 15 is provided in the main drill body 11 and branch passages 16 and 16a connect this main passage respectively Withdistributing channels 17 and grooves 17a provided in the abrading portions 12 and 13 of the drill body 11. These passages 16 and 16a and channels 17 and grooves 17a serve to distribute water over the abrading surfaces to promote efficient chip removal and heat dissipation. Y,

An auxiliary drill bit body'18 whosedi-ameter at its abrading surface portions .19 is somewhat greater than the radius of the main drill bit at its abrading surfaces drill string (not shown).

12 and 13 is adapted to be supported in freely rotatable manner within the main drill bit body 11. Abrading device embody- 12 and 13 in any conventional manner 2,911,196 Patented Nov. 3, 1959 relationship with abrading surface 12 or projects a small amount c below the latter and so that its peripheral abrading surface 20 extends beyond the geometrical center or axis of the main drill bit 11 and so that its peripheral surface 20 is substantially tangent to or extends slightly beyond the periphery of the main drill abrading surface 13.

The auxiliary bit body 18 is supported rotatably within the main drill body. 11 by a combination radial and thrust bearing 21, which may be either a journal bearing or anti-friction roller bearings 22 as shown. The auxiliary bit body 18 is maintained in position within body 11 as by a spring retainer ring 23 located in an annular groove 24 in said body. This ring 23 also serves to resist hung-up forces from pulling the auxiliary bit body 18 out during removal of the bits from the hole drilled by them.

An axial passage 25 in the auxiliary bit body 18 communicates with the main water channel 15 in the main bit body 11 as by a passage 26 and with channels 27 in the face of bit body 18 to promote efficient chip removal and heat dissipation.

In operation, the main drill body 11 is attached to the lowermost end of the drill string (not shown) and lowered into the hole for drilling. On rotary drive, of

the drill string and bit body 11, the forces tending to excess of the radius of the main bit, positive drilling is effected at the geometric center of the main drill bit by the drilling surface 19 of the auxiliary drill bit 18 which thus has a substantial velocity over the rock surface that it is intended to cut.

While a specific embodiment of the invention has been shown and described, variations in structure within the scope of the appended claim are possible and are contemplated. There is no intention, therefore, of limitation to the exact details herein shown and described.

What is claimed is:

In combination, a main drill bit having an abrading surface and having a generally longitudinal recess eccentric of its longitudinal axis, a freely rotatable auxiliary drill bit having an abrading surface and being carried by said main drill bit within said recess so that its periphery overlaps the geometric center of said main drill bit,

combination radial and thrust bearing'means within said recess for rotatably supporting said auxiliary. drill bit within said recess so that the said two abrading surfaces lie in substantially co-planar relationship, and retaining ring means interior of said recess for preventing separation of said auxiliary drill bit from said main drill bit during their extraction from a hole drilled by them, the said main drillbit having a main passage and branch passages in communication therewith and the said auxilw iary drill bit having an axial passage therein communicating with said main passage for distribution of drilling fluid to the said abrading surfaces during a drilling operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,814,296 I Dean July 14, 1931- 1,858,282 Scott May 17, 1932 2,511,831 Adamson June20, 1950 2,667,334 Ortlofi Jan. 26, 1954 

